Excitation and Emission Spectra of Cs2NaLnCl6Crystals Using Synchrotron Radiation

ABSTRACT The visible emission and vacuum ultraviolet excitation spectra of the series Cs2NaLnCl6 (Ln = Y, Nd, Sm, Eu, Tb, Er, Yb) and Cs2NaYCl6:Ln3+ (Ln = Sm, Er) have been recorded using synchrotron radiation at room temperature, and in some cases at 10 K. The excitation spectra comprise features associated with charge transfer, excitation from the valence to conduction band, and impurity bands. No d–f emissions were observed for these Ln3+ ions, so that the emission bands comprise intraconfigurational 4f N –4f N transitions and impurity bands, whose natures are discussed. Theoretical simulations of the f–d absorption spectra have been included. The comparison with data from the synchrotron at Desy enables a comprehensive account of the ground (or vibrationally excited ground for Ln2+) states of the Ln3+ 4f N , Ln3+ 4f N−15d, and Ln2+ 4f N+1 configurations relative to the valence and conduction bands of Cs2NaLnCl6, for which the band gaps are between 6.6 and 8.1 eV. KEYWORDS: 4f–5d spectracharge transferenergy levelsexcitation spectralanthanide ionspectral intensities ACKNOWLEDGMENTS Financial support for this work from the Hong Kong Research grants Council General Research Fund Grant City U. 102308 is gratefully acknowledged. This work was also supported by the National Science Foundation of China, under Grant 10874253. Notes Note. Refer to the text for explanation. Note. The units are 103 cm−1. SF = spin-forbidden. The energies relate to SF transitions. Refer to the text for explanation. a From Ref. [29], relative to Ce3+ b From Eq. (Equation3). c From Ref. [30], relative to Eu3+. d From Eq. (Equation4). e This work. f Following Ref. [32]: 0.5 eV (4033 cm−1) has been added to the peak maximum in this region of the room-temperature excitation spectrum. This may be an under-estimation. Starred values are from 10 K spectra. The value for Pr3+ is from Ref. [26]. g Ref. [11] at 10 K. h Ref. [26] at 10 K. i Ref. [27] at 295 K and revised herein. j Ref. [10]. k Ref. [28] at 10 K. l Ref. [48].